Field of the Invention
The present invention relates to a magnetic toner that is used in a recording method that relies on electrophotography, electrostatic recording or magnetic toner jetting.
Description of the Related Art
Developments in image-forming apparatuses such as copiers and printers in recent years have placed greater demands on toner, in terms of coping with higher speeds, better image quality and higher reliability, at or above the level of conventional image-forming apparatuses. As the environments in which toner is used have become more diverse, toner is furthermore required to afford stable images also when used in such various environments.
Meanwhile, one-component development schemes are preferably used as development schemes in such image-forming systems, since one-component development is little problematic, and boasts long service life and easy maintenance, and can therefore be used in a developing device of simple structure.
Such one-component development schemes include various known methods. One such method is jumping development relying on magnetic toner wherein a magnetic iron oxide is encapsulated in the toner. Jumping development is a method that involves causing a magnetic toner charged through triboelectric charging with a toner carrying member to fly onto and become adhered to a photosensitive member, on account of a developing bias, and developing thereupon the electrostatic image on the photosensitive member in the form of a magnetic toner image. Jumping development is widely used in practice thanks to the ease with which transport of the magnetic toner is controlled, and thanks to the low degree of internal contamination that jumping development generates in a copier, printer or the like.
Several methods have been proposed in the past for obtaining stable images through the use of magnetic toner of high degree of blackness.
Japanese Patent Application Publication No. H06-118700 discloses a feature of prescribing a ratio between the dielectric loss tangent of toner at a high-temperature region and at a normal-temperature region, and using a colorant of high degree of blackness, to reduce thereby changes in the charging performance of toner caused by the environment, and maintain as a result high degree of blackness also in a halftone image, regardless of the environment.
Japanese Patent Application Publication No. 2009-205047 discloses a toner in which the surface of a toner carrying member exhibits no contamination, even upon printing over long periods of time, through control of the particle size distribution of the toner and of uneven portions at the toner carrying member surface.
Japanese Patent Application Publication No. 2008-230960 discloses a method of producing a magnetic iron oxide of high degree of blackness, through control of a sulfur component within the magnetic iron oxide, and discloses a magnetic toner of good tinge that comprises the above magnetic iron oxide.